1. Technical Field of the Invention
The present invention relates in general to the exchange of network information in a communications system, and in particular to data recovery in connection with pre-paid telecommunications services.
2. Description of Related Art
In accordance with most cellular service plans, cellular service providers charge for mobile telephone services on a monthly basis. Accordingly, the service providers keep track of the amount of time each subscriber uses his or her mobile telephone during a one month period. Then, at the end of the month, the service provider bills the subscriber based on his or her usage during that month.
Generally, cellular service plans are billed at a flat rate that allows the subscriber to use his or her mobile telephone for a certain number of minutes each month without incurring additional charges. Thus, if the subscriber""s usage is at or under the allowed number of minutes (i.e., the included minutes), the subscriber simply pays the flat rate for that month. On the other hand, if the subscriber uses more than the number of included plan minutes, the subscriber pays a per minute charge for the excess minutes. In either scenario, additional charges may also apply depending on the type of calls that are made or received by the subscriber. For example, separate long distance and international charges generally apply, and subscribers might also be subject to additional charges for calls that are made or received when the mobile telephone is xe2x80x9croamingxe2x80x9d (i.e., when the subscriber is outside of a defined home service area or is in an area served by a different cellular service provider).
As a cellular telephone call is routed through the network during call set-up, and thereafter handled, the switching nodes involved in the call generate billing records containing charging data relating to the ongoing cellular call. This charging data includes details concerning the call such as an identification of the calling and called parties, party location information, routing information, switching information, and other call related information. In order to differentiate between the many cellular calls being handled, and to reconcile multiple billing records between different network elements to properly charge for each individual cellular telephone call, each call is assigned a unique billing identification number. Based on the signaling, this billing identification number may be provided along with the charging information in each billing record report sent by a switching node to the billing center. The billing center stores this information for use in calculating whether the subscriber has exceeded his or her included plan minutes for that month and whether any additional charges apply.
In connection with the ongoing development of Wireless Intelligent Network (WIN)-phase 2, new charging services are being designed. For example, WIN-phase 2 is being designed to offer pre-paid accounts for mobile subscribers. A pre-paid account allows a mobile subscriber to pre-purchase a certain dollar amount of cellular telephone services. In contrast to a conventional cellular service plan, in which included plan minutes that are not used in a particular month are lost, a pre-paid account balance is typically carried over from month to month until it is fully depleted based on the number, length, and type of calls that are made or received by the cellular subscriber. Depending on the service agreement, however, there may be a time limit on how long the balance can be carried over. In addition, account information associated with a pre-paid account is maintained at a service control point (SCP) in the operator""s network. The SCP, for example, maintains account balance information, the number of minutes left for a particular calling rate, and ordering information for additional pre-paid purchases. In connection with call set-up and during a subsequent ongoing call, the SCP deducts money (or time, or credit) from the account balance at an appropriate rate for the particular type of call.
Because the SCP nodes control all of the account information for a particular mobile telephone, however, the SCP nodes contain fairly sensitive information from an account perspective. Failures in the network might result in the SCP being unaware of events involving the mobile telephone, such as call originations or terminations. Such failures can cause significant inaccuracies in the billing information maintained in the SCP by, for example, permitting the cellular subscriber to use cellular services without being charged (i.e., a runaway call) or causing the subscriber""s balance to be erroneously depleted (i.e., runaway charging). Similar billing inaccuracies can also result in cases of an SCP restart or a restart of some other node in the network that causes a loss of data.
In the case of a runaway call, a cellular service provider is essentially providing services without collecting revenue, thereby reducing profitability for the service provider. In the case of runaway charging, on the other hand, a subscriber is essentially being charged for services that have not been provided, which, if not corrected, can result in customer dissatisfaction. Thus, cellular service providers have an interest in avoiding both runaway call and runaway charging situations. When certain portions of the network that are critical to maintaining accurate account balance information are out of service, however, it can be difficult or impossible to avoid charging errors. There is a need, therefore, for a system and method for recovering data relating to pre-paid subscriber accounts when a portion of the cellular network is out of service for a more than an inconsequential period. Such a method and system would allow charging errors to be corrected or otherwise accounted for as soon as possible after the service outage is discovered.
The present invention comprises a method and system for automatically adjusting charges to a pre-paid account balance following a temporary failure in a network. In accordance with normal pre-paid telephone service operating procedures, a call connection or other xe2x80x9con demandxe2x80x9d telecommunications service is initiated (e.g., in response to a call set-up request). In the context of pre-paid cellular service, these call connection services and other types of services are charged against an account balance for a subscriber station having a pre-paid service agreement. Charging operations are performed by a charging node in the network.
In accordance with one embodiment of the invention, the call connection or other service is terminated during a temporary failure in the network, such as a failure of a switching node or charging node. The failure prevents the charging node from being informed of the service termination until after the failure has been corrected. After a recovery from the failure, a message is sent to the charging node containing call connection termination information or other service termination information. Based on the received termination information, the charging node adjusts the account balance for the subscriber station. Preferably, the adjustment involves computing the time for which the call or other service was provided to the subscriber and adjusting the account balance such that the total amount charged for the call or other service corresponds to the computed time.
In accordance with another embodiment of the invention, a fault recovery process is performed in connection with a mobile switching center (MSC) failure that causes all of the calls being handled by that MSC to be dropped. Once the MSC recovers, it sends a termination information message to the charging node indicating that an MSC failure occurred and indicating the time at which the failure occurred. As a result, the charging node adjusts the account balance based on the received termination information, thereby preventing runaway charging.
In another embodiment of the invention, a charging node failure occurs that temporarily prevents the charging node from receiving service termination information. Once the charging node recovers from the failure, it requests a status update from its associated switching nodes. In response, each switching node returns a list of all active calls handled by that switching node. If the list received by the charging node does not include a particular previously initiated call for which no termination notification has been received, such absence of the call from the list constitutes an indication that the call was terminated during the failure. On the other hand, if the list received by the charging node does include a particular previously initiated call, the charging node knows that such call is still ongoing and can continue charging for the call. Using this procedure, runaway charging and runaway calling can be avoided. In particular, this procedure prevents the charging node from continuing to charge for calls that were terminated during the charging node failure, thereby preventing runaway charging. Similarly, this procedure allows the charging node to continue charging for calls that are still ongoing, thereby preventing a runaway call.
In accordance with an alternative embodiment, a switching node stores termination information for call terminations that occur during a charging node failure and that are not acknowledged by the charging node. After recovery from the failure, the charging node requests a status update from its associated switching nodes. In response to the status update request, the switching node returns data indicating which calls were terminated and the time at which the termination occurred. Using this information, the charging node adjusts the account balance to account for the termination, thereby preventing runaway charging and runaway calls.